Relation between the intrinsic RV scatter, rms_RV(τ = 14days), age, and T_eff for stars observed in the RVSPY high-cadence programme. T_eff is coded in colour. Stars marked as triangles do not have significant IR excess (see Sect. 3.1). The black dashed line shows the relation derived by Brems et al. (2019, their Eq. (5) with parameters for model (a) from Table 3) for τ = 14 days. The thick orange dashed line shows the same relation with є modified from 1.382 to 0.93, adapted to our sample (see text). The horizontal dashed-dotted line marks the approximate boundary above which we consider RV exoplanet searches not feasible (although we use a mass detection threshold in the end; see Sect. 7.5 and Fig. 11).